# std::filesystem::rename

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< cpp‎ | filesystem

Defined in header `<filesystem>` |  |
void rename( const std::filesystem::path& old_p, const std::filesystem::path& new_p ); | (1) | (since C++17)
void rename( const std::filesystem::path& old_p, const std::filesystem::path& new_p, std::error_code& ec ) noexcept; | (2) | (since C++17)

Moves or renames the filesystem object identified by old_p to new_p as if by the POSIX `rename`:

- If old_p is a non-directory file, then new_p must be one of:

  - the same file as old_p or a hardlink to it: nothing is done in this case.
  - existing non-directory file: new_p is first deleted, then, without allowing other processes to observe new_p as deleted, the pathname new_p is linked to the file and old_p is unlinked from the file. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.
  - non-existing file in an existing directory: The pathname new_p is linked to the file and old_p is unlinked from the file. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.

- If old_p is a directory, then new_p must be one of:

  - the same directory as old_p or a hardlink to it: nothing is done in this case.
  - existing directory: new_p is deleted if empty on POSIX systems, but this may be an error on other systems. If not an error, then new_p is first deleted, then, without allowing other processes to observe new_p as deleted, the pathname new_p is linked to the directory and old_p is unlinked from the directory. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.
  - non-existing directory, not ending with a directory separator, and whose parent directory exists: The pathname new_p is linked to the directory and old_p is unlinked from the directory. Write permissions are required to both the directory that contains old_p and the directory that contains new_p.

- Symlinks are not followed: if old_p is a symlink, it is itself renamed, not its target. If new_p is an existing symlink, it is itself erased, not its target.

Rename fails if

- new_p ends with dot or with dot-dot.
- new_p names a non-existing directory ending with a directory separator.
- old_p is a directory which is an ancestor of new_p.

### Parameters

old_p | - | path to move or rename
new_p | - | target path for the move/rename operation
ec | - | out-parameter for error reporting in the non-throwing overload

### Return value

(none)

### Exceptions

Any overload not marked `noexcept` may throw std::bad_alloc if memory allocation fails.

1) Throws std::filesystem::filesystem_error on underlying OS API errors, constructed with old_p as the first path argument, new_p as the second path argument, and the OS error code as the error code argument.
2) Sets a std::error_code& parameter to the OS API error code if an OS API call fails, and executes ec.`clear`() if no errors occur.

### Example

Run this code

    #include <filesystem>
    #include <fstream>
    namespace fs = std::filesystem;

    int main()
    {
        std::filesystem::path p = std::filesystem::current_path() / "sandbox";
        std::filesystem::create_directories(p / "from");
        std::ofstream{ p / "from/file1.txt" }.put('a');
        std::filesystem::create_directory(p / "to");

    //  fs::rename(p / "from/file1.txt", p / "to/"); // error: "to" is a directory
        fs::rename(p / "from/file1.txt", p / "to/file2.txt"); // OK
    //  fs::rename(p / "from", p / "to"); // error: "to" is not empty
        fs::rename(p / "from", p / "to/subdir"); // OK

        std::filesystem::remove_all(p);
    }

### See also

rename | renames a file (function)
removeremove_all (C++17)(C++17) | removes a file or empty directory removes a file or directory and all its contents, recursively (function)

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